Larry Emme Chemeketa Community College

1. Solutions Chapter 14 Larry Emme Chemeketa Community College

2. General Properties of Solutions

3. A solution is a system in which one or more substances are homogeneously mixed or dissolved in another substance. • The solute is the component that is dissolved or is the least abundant component of the solution. • The solvent is the dissolving agent or the most abundant component in the solution.

5. Properties of True Solutions

6. The mixture of two or more components–solute and solvent –is homogeneous and has a variable composition. • This means that the ratio of solvent to solute can be varied. • The dissolved solute is molecular or ionic in size. • It is either colored or colorless and is usually transparent.

7. The solute remains uniformly distributed throughout the solution and will not settle out with time. • The solute can generally be separated from the solvent by purely physical means such as evaporation. • The solute particles of a true solution are molecular or ionic in size. • The particle size range is 0.1 nm (10-8cm to 1 nm (10-7cm).

8. Colloids: An Introduction

9. colloid A dispersion in which the dispersed particles are larger than the solute ions or molecules of a true solution and smaller than the particles of a mechanical suspension.

10. suspension a dispersion in which microscopically visible particles are mixed with, but not dissolved in a fluid or solid.

11. Colloid is derived from the Greek word “kolla” meaning “glue.” • The term colloid does not imply a system has a gluelike quality.

12. In ordinary solutions the size of solute particles range from 0.1 to 1 nm. • The size of colloidal particles range from 1 to 1,000 nm. • In a solution the particles are usually single ions or molecules. • In a colloid the particles are usually aggregations of ions or molecules. • The fundamental difference between the particles of a colloidal dispersion and a colloid is the size of the particles.

13. Dispersions and Suspensions • A solution is a stable, homogeneous mixture. • A dispersion (colloid) is stable to gravity, but can be separated by centrifugation or filtration. • A suspension contains larger particles that will settle over time.

14. Types of Colloidal Dispersions

15. Properties of Colloids

16. Tyndall Effect in Dispersions Light passing through a solution (left) is not scattered, but the larger particles in a dispersion (right) deflect some of the light.

17. Colloidal particles have huge surface areas in comparison to the volume of the same particles if they were aggregated into one large particle. • Colloidal particles become electrically charged when they adsorb ions on their surfaces. • This occurs because surface atoms or ions attract and adsorb ions or polar molecules from the dispersion medium.

18. Solubility

19. Solubility describes the amount of solute that will dissolve in a specified amount of solvent.

20. Solubilities of substances vary widely.

21. Terms that describe the extent of solubility of a solute in a solvent: • very soluble • soluble • moderately soluble • slightly soluble • insoluble

22. miscible: liquids that are capable of mixing and forming solutions. • Terms that describe the solubility of liquids: ethyl alcohol and water • immiscible: liquids that are insoluble in each other. oil and water

23. Solubility of Various Common Ions in Cold Water

24. General Solubility Rules for Common Ions

25. Factors Related to Solubility

26. Factors that affect solubility are • ion size • interactions between solute and solvent • temperature

27. The Nature of theSolute and Solvent

28. The general rule for predicting solubility is “like dissolves like”.

29. SolventPolarity • Polar compounds tend to be more soluble in polar solvents than nonpolar solvents. • NaCl (sodium chloride) is • soluble in water • slightly soluble in ethyl alcohol • insoluble in ether and benzene

30. The hydrated ions slowly diffuse away from the crystal to become dissolved in solution. As the attraction between the ions weakens, the ions move apart and become surrounded by water dipoles. Polar water molecules are attracted to Na+ and Cl- ions in the salt or crystal, weakening the attraction between the ions. Dissolution of sodium chloride in water.

31. Hydration Polar water attracts to Na+ and Cl– ions

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42. Barium Sulfate BaSO4

43. SolventPolarity • Nonpolar compounds tend to be more soluble in nonpolar solvents than in polar solvents. • benzene or cyclohexane is: • insoluble in water • soluble in ether

44. The Effect ofTemperature on Solubility

45. Most solutes have a limited solubility in a specific solvent at a fixed temperature.

46. Effect of Temperature on theSolubility of a Solid in a Liquid • For most solids dissolved in a liquid, an increase in temperature results in increased solubility. • Some solids increase in solubility only slightly with increasing temperature. • Some solids decrease in solubility with increasing in temperature.

47. large increase in solubility with temperature slight increase in solubility with temperature decrease in solubility with increasing temperature

48. Effect of Temperature on theSolubility of a Gas in Water • The solubility of a gas in water usually decreases with temperature. • Kinetic molecular theory accounts for this decreased solubility. • For the gas to dissolve it must form bonds of some sort with the molecules of the liquid. • At higher temperatures the kinetic energy of the gas molecules is sufficient to break the gas water bond.

49. large decrease in solubility with increasing temperature

50. The Effect ofPressure on Solubility